Process of producing alloy steels



UNITED STATES PATENT OFFICE.

CHARLES H. JOHNSON, OF AVALON, PENNSYLVANIA.-

PROCESS OF PRODUCING ALLOY STEELS.

No Drawing.

covered certain new and useful Improve-- ments in Processes of Producing Alloy Steels, of which improvements the followin 'is a specification.

y invention proceeds from the discovery that allqy steels may be roduced in un1nterrupte operation, beginning with lI'OIl oxid in the form of ore or scale; the smelt-- ing operation is accomplished in the presence of both ferro-silicon and ferro-chromium, and such other non-ferrous metals as ma be desired in the ultimate alloy are ad' ed in the form either of oxids; or of ferro-alloys, or of both. While not so specifically llmited, my invention finds practical application to the production of highspeed steel, and I shall describe it in that particular application; its applicability, however, to a wider field will be understood, and in certain of the claims I shall define it in its wider scope and aspect.

In the narrower field of high-speed steel I have practised my invention with notable advantage in the following particulars: First of all, reduction of such refractory material as high-speed scale, carried out in the presence of both ferro-silicon and ferrochromium, becomes a much simpler operation; the smelting operation proceeds at a much lower temperature than otherwise would be possible, and with consequent gain in the matters of fuel consumption and of wear and tear upon the furnace." Highs eed scale is the scale which comes from jtlie fabrication of articles of high-speed steel. It is an undesired byproduct. Though rich in. the valuable metals alloyed with the steel-tungsten, for example, commonly present in amounts as great as 11 or 12%, and vanadium in smaller amounts (about .4%),it still has heretofore been so difficult of and so expensive of reduction, that in the eye of the steel maker it is of little value, and little better than a waste product. These difiiculties'I overcome, and with manifest gain.

A second advantage lies in this; that,in,

Specification of Letters Patent.

Patented Jan. 25, 1921.

Application filed December 12, 1919. Serial No. 844,329.

consequence of the lower temperature conditions prevailing during the smelting operation, the carbon component of the furnace charge (and, accordingingly, of the finished product) may be kept low and kept under control, and, at the same time, when operating upon high-speed scale, all or substantially all of thermore valuable alloymg metals presentvanadium, tungsten, chromlum, etc., may be conserved. And, resulting from this, it follows that high-speed steel may be produced in uninterrupted operation, beginning with lii h-speed'scale, or other raw material. This is a procedure not heretofore attained, and commonl thought to be unattainable. The usual wag is to begin with a derived material of relatively low grade, ordinarily in high-speed steel ,work a low grade ferro-tungsten containing vanadium. This derived material is the only product which heretofore has-been derived from high-speed scale by direct operation.

It is called melting .bar, although it is not always inbar form. It is with this intermediate material that the production of high-speed steel, as such, ordinarily begins and, beginning with it, processes of refining and of building up the desired alloy proceed. As I have now made abundantly plain, my invention begins, not with the intermediate product, but with the raw,material out of which that intermediate product has previously been derived, that is to say, with iron oxid (which may be high-speed scale), and proceeds thence 1n uninterrupted operation to the ultimate product, highspeed steel.

A third advantage of the application of my invention to high-speed steel production lies in the incidental discovery of a steel of new composition, having individual characteristics, relatively inexpensive, but in performance excelling the most expensive highspeed steels of the present day. ThiSfsteel of new composition, hereinafter disclosed, I make the subject of an independent application for Letters Patent, Serial No. 344,330, filed December 12, 1919.

The results which I have attained are consequent upon a long series of experiments, to the'ordering of which" has gone much thought, and in the course of which advantage has been taken of discoveries, both direct and incidental.

I can best describe my invention by rehearsing my actual operation, conducted on a scale whichdmparts to them an experimental aspect, although they are in constant and continuing use for commercialpurposes.

It will be understood that the actual performance is here given as a typical example,

showing how my invention may be applied;

latitude is permissible; this operationneed' not be slavishly followed. I shall, in the ensuing claims, define What is essential; and, so long as those essential things be adhered to, my invention" will be practised, even though there be-variation in other respects.

My initial furnace charge, of the actual operation alluded to, is

-High-speed. scale, 300 pounds, Ferro-chromium, 20 pounds, Ferro-silicon, 27 pounds, Charcoal, 46 pounds, Molybdenum, 21 pounds, and

Tungsten, 4% pounds.

The ferro-chromium and ferro-silicon are broken; up and mixed together, and then mixed with the scale which constitutes the body of the furnace charge. The molybdenum and tungsten additions are made, and their quantities are determined, according as the scale is rich orpoor in these ingredients and capable or incapable of at, fording all that is needed in the finished' product. The molybdenum which I intro duce is of 7 8% purity and is in the form of powder; the tungsten also is in powdered- These alloyform and is of 82% purity. ngtmetals are introduced .(if at all) in'the initial charge, rather than in subsequent additions, because (and this is peculiarly true of the tungsten), when so introduced, they do not. in any appreciable degree enter into the slag, as'ls their tendency to do, if subsequently added.

The furnace" charge so constituted, is

brought to smelting temperature and the desired reactions ensue; the operation in this respect-is the usual' one, and further descnptlon is unnecessary.

Incidental to or, more properly speaking,

consequent upon the smelting reactions, I find opportunity to bring the carbon component to the desired value. It is in anticipation of this that I keep the carbon constituent of the initial charge low (lower than suificient toafi'ord to the finished product itsde'sired carbon content). When the smelting reactions have taken place, I sample the metal of the molten bath; allowing the samplesto grow cold, I subject them to fracture test, and udge thereby, whether the carbon content be proper. If it be too low,,

(as I intend and prefer it shall be) I build up the carbon content by chargin in coke and stirring it into the bath.

nder this procedure the bath beginsto carbonize at moderate speed, and, maklng tests at intervals of l0or 15 minutes, I proceed until .by fracture test I}find the carbon content to have increased to the desired value.

Specifically; I get best results when I so proportion the initial charge that, when testing begins, the carbon contentis in value .08 to 20% and I proceed with the addition of coke until the value risesto about .50%. Itis .best' to begin with carbon low and then'to build it up, because in so adding coke I incidentally restore to the bath the vanadium which initially has entered the slag.-. In case I find on the first test that the carbon content is high-Pas high as or higher, let us say, than is ultimately preferable- .60% or more, I do not on that account abandon the ,furnace charge; I. charge in more scale, rather, until I have reduced the carbon to the preferred minimum of the normal operation (approximately .08%), and thence I proceed with the building up of the carbon, in the manner already described.

Having so brought the carbon component of the bath to the desired value, it remains only to make certain final additions (not always made, however, as I shall presently explain), to bring the silicon, manganese and vanadium components to the desired Values. These, in the actual operation I am describing, ar e- Ferro-silicon, 3 pounds, Ferro-manganese, 2 pounds, and Ferro-vanadium, 5:} pounds.

,, Tapping ensues.

I said ,a moment ago that final additions such as those'just enumerated will not al-' v ways be made. If, because of the composition of the scale used, the desired composi-- tion of-the ultimate product may be had without these final additions, then of course,

these Will'not be made. To be specific, in

the case under consideration, ifthere be no final additions, the chromium content of the finished product will range from a few.

tenths of one per cent. to 5%tungsten; from 12 to 13%; and vanadium, from .30 to .40%

. and this may conceivably meet the specifications in hand.

Returning however to consideration of the operation as I normally and preferably conduct it, it remains to define the composition of the finished product, so far as concerns the elements which give it character as a concerns definition of my invention. I add that the steel ofthis composition is in certain distinguishing and characteristic feature new, and is itself the subject of a separate application forLetters Patent.

The operation now described is preferably carried out in an electric furnace, and (again by way of illustration, and not limitation) I shall define in specific terms what actually I use. The furnace is built with a steel shell in which is rammed a linin compounded of magnesite, some slag, an enough tar tobringit to pro er consistency- The electrodes are intro need through to and bottom; those through the top preferably there are several) extend down to the slag; those through the bottom are exposed to contact of the bath. These bottom electrodes'are steel rods screwed into a copper plate and tamped about with the same'lining material defined above. The furnace ma be stationary or tilting; the furnace which is the basis of this description isstationary, and the metal is tapped from it into a ladle from which it runs into the ingot mold.

The furnace I employ has capacity suf: ficient to produce an ingot of about 200 pounds weight. My current is supplied at a pressure of 40-45 volts. Giving again specific figures, a run of my operation continues through 6 to 7 hours; starting with a cold furnace, the consumption of current fora single run is approximately 400 kilowatthours. The current used may be singlephase or polyphase.

The ingot obtained in the particular run tabulated weighed 225 pounds, and in additioIi the test pieces aggregated 15 pounds.

I have said that my invention is applicable to the production of other steel alloys. That is to say, starting with iron ore or scale, and using the ferro-silicon-ferrochromium mixture, which is the essence of the invention, the desired alloy may be pro- ,duced by adding (if addition be necessary), the still requisite non-ferrous ingredientsnickel, chromium, vanadium, tungsten, cobalt, molybdenum, tantalum, zirconium, or what one will, in the form of oxid or of ferro-alloy. I

I claim as my invention:

1. An improvement in the method of conducting the operation of smelting iron oxid which consists in introducing into the charge of the smelting furnace both ferrosilicon and fend-chromium.

2. An improvement in'the method of reducing high-speed scale which consists in submitting it to the smelting operation when mixed with both ferro-silicon and ferrochromium.

3. The herein described method of prosmeltin ducing high-speed steel which consists in smelting high-speed scale in the presence of both ferro-silicon and ferro-chromium, and in adding to the resultant bath an alloying metal of such nature as to enter in and give chail'acter to the product as a high-speed stee 6. The herein described method of 'producing high-speed steel which consists in smelting high-speed scale in the presence of both ferro-silicon andferro-chromium, and in adding to the resultant bath ferro-vanadium. a

7. The herein described method of producing high-speed steel which consists in smelting high-speed scale in the presence of both ferro-silicon and ferro-chromium, and in adding to the resultant bath a ferrocompound of an alloying metal of such nature as to enter in and give character to the product as a highspeed steel. I

8. The herein described method of producing high-speed steel which consists in smelting high-speed scale in the presence of 5 both ferro-silicon and ferro-chromium, to-.

gether withnn alloying metal, and in adding to the resulting bath an alloying metal of such nature as to enter in and give character to the product as a high-speed steel.

9. The herein described method of producing high-speed steel which consists in smelting in the presence of both ferro silicon and ferro-chromium a body of high-speed scale, and subsequently building up the carbon content of the resultant bath. V 10. The herein described method of producing high-speed steel which consists in smelting a mixture of high-speed scale,

ferro-silicon, ferro-chromium, and carbon,

-the amount of carbon being insufiicient to afford the desired carbon content of the finished product, building up the carbon content of the resultant bath, and finally adding to the bath an alloying metal of such nature as to enter irrand give character to the prod-Q. not as a high-speed steel.

11. The herein described method of producing high-speed. steel which consists in smelting a mixture of high-speed scale, ferro-silicon, ferro-chromium, and carbon, the amount of carbon being insufficient to afford the desired carbon content of the finished product, and building up the carbon content in the resultant bath by introducing coke through the slag upon the'bath in the furnace.

memes 12. The herein described method of prowhich consists in introducing into the ducing high-speed steel which consists in charge of the smelting furnace ferro-silicon, smelting a mixture of high-speed scale, ferro-chromium. and carbon. ferro-silicon, ferro-chromium, and carbon, In testimony whereof I have hereunto set 5 bringing the carbon content to a desired my hand.

transient value by additions of high-speed scale, and building up thence the carbon content of the bath. Witnesses: 13. An impro'vement'in the method of con- BAYARD H; CHRIs'rY, 10 ducting the operation of smelting iron oxid FRANCIS J.v TomAssoN.

CHARLES M. JOHNSON. 

